US2281494A - Clock - Google Patents

Description

April 23, 1942- L. HAMMONDy 2,281,494

ycLocx Filed Feb. 15, 1931 5 sheets-sheet 1 April 28, v1942- L. HAMMOND 2,281,494

. CLOCKr Filed Feb. 13. 1931 s sheets-sheet s 1 7&6 m7747707@ 4a@ 762 -77 l 37.3 400 772 .7546@ @Mi l -Y-(D 24 76! 7% m :3U 176i? /404 776 75g: 70a 92 a6 64 2 77@ .77d 774 a? l 1 /40 114 Y zzz e u im I 1%@ 5% i 74 70 22 120 1r v+m 7 742 74o" 7 754 i i@ 756 f4? April '28, 1942. L. HAMMOND CLOCK,

Filed Feb. 13, 1931 5 Sheets-Sheet 4 April 23, 1942 L. HAMMOND 2,281,494

' CLOCK Y Filed Feb. 13, 1931 5 Sheets-Sheet 5 y//M' 32% I Patented Apr. 28, 1942 CLOCK Laurens Hammond, Evanston, lll., assigner to Hammond Instrument Company, Chicago, lll., a corporation of Delaware Application February 13, 1931, Serial No. 515,599

33 Claims.

My invention relates generally to time-keeping devices and more particularly to mechanical speed governing means especially usable in combination with synchronous electric cloclts.

Synchronous electric clocks have come into general use because of their simplicity, durabilityLquiet operation, and high degree of accuracy. These clocks generally comprise an ordinary clocl-r gear train driven by a synchronous motor and, as at present on the market, have the pronounced disadvantage that they stop upon interruption of the supply of alternating current. Several means for overcoming this disadvantage have beenproposed but have not come into general use because of their commercial impracticability, even though the demand for a clock which will not stop upon interruption of drive being held againstoperation while the synchronous motor was in operation and vice versa. This attempted solution had the same disadvantages as enumerated above except that instead of "losing time the clock would gain. time. The reason for this gaining of time was that it always took a certain amount of time to stop one of the mechanisms and start the other, and hence there was a certain amount of the supply of current is very great. In some communities interruptions occur at frequent intervals, due to electrical storms, shut-downs 'm the power generating stations, and disconnections in the` transmission lines necessary for repairs and alterations. Even in communities where the supply of current tcY the consumeris only very rarely interrupted, the supply of current to the individual clock is frequently interrup'ted due to the accidental disconnection of the plug from the socket through which the clock respring motor driven clock mechanism which served as a standby movement to drive the hands of the clock upon interruption of the current, suitable clutch and stop vdevices being incorpo- .rated to cause operation of the clock by the standby movement upon interruption of the current supply to the synchronous motor. This attempted solution of the problem presents diniculties in manufacture, greatly increases the cost of the clocks, and is not entirely successful in operation because of the fact that a certain amount of time is lost each time the transfer is made from the synchronous motor drive to the spring motor drive. y

Another attempted solution involved the provision of a synchronous motor drive and spring motor drivevconnected through differential gearingwith the hands of the clock, .the spring motor overlap during which interval both mechanisms were operating, thus permitting the differentially movable member of Vthe differential gearing to move twice its normal speed during this interval. In the clock of thevpresent invention there is no auxiliary clock movement.- Generally, the

clock comprises an induction motor geared to wind a spiral clock spring, the driving side of which is geared to a synchronous electric brake which acts in place of the escapement mechanism of an ordinary clock, and prevents the spring from unwinding at greater than a predetermined speed. The rotating part of the synchronous electric brake is also connected to a centrifugal mechanical speed governing mechanism, a pawl and ratchet mechanism preventing the spring from unwinding and rotating the induction motor backward when the current supply -is interrupted. inasmuch' as the synchronous electric brake is ineffective to control the speed of operation during an interval of current interruption, the centrifugal governing mechanism is so constructed that it is at all times effective to take over the speed governing function.

VIt will be understoodthat power generating stations supplying so-called time service," regulate the frequency of the current supplied so that the average frequency during any extended period of time will always exactly equal the nominal frequency.` For example, in a station supplying current at a nominal frequency of 6G cycles per second, the frequency may vary between 57 cycles and 63 cycles per second. In a large, well-regulated station the range of variation may often be reduced to between 59.8 and 60.2 cycles per second. Occasionally, especially in the smaller power generating stations, the frequency will drop gradually to a very low value due to the sudden addition of a large load upon the generator, or in fact. the frequency may drop gradually from 60 to 0 if the generator is slowed down due to accident or for repairs.

Itis essential, in providing'a mechanical speed governor for use in connection with'a synchronous electric cloclcvor similar device, that it does `not interfere with the operation of the clock upon such normal variations in the frequency of the current supply, since ordinarily compensation is made for such variations by increasing or decreasing the generator speed above or below the nominal frequency for a sufficient period of time to bring the average frequency 'back to the nominal frequency. A further requirement of a mechanical speed governing mechanism for use in controlling the speed of a clock or similar device during current interruptions, especially when used in connection with a clock which is not selfstarting, is that the mechanical governor maintains the speed so close to the nominal frequency that upon resumption of the current supply the synchronous motor will again fall into step, or that the speed of operation be periodically varied between frequencies above and below the nominal'frequency so that at regular intervals the clock will be operating at exactly synchronous speed and will have an opportunity to fall in step when the current supply is resumed.

The mechanical speed governing mechanism of my invention operates upon the latter principle, namely, permitting the clock alternately to accelerate and decelerate between definite limits above and below the nominal speed.y

In addition to the objects above pointed out, the objects of my invention are to provide an electric synchronous clock which (l) Will operate at constant average speed during periods of current interruption;

' (2) Will not require manual rewinding;

(3) Utilizes a synchronous electric brake to control its speed of operation when current is being supplied to it;

(4) Has a centrifugal continuously-rotating mechanical means automatically operable ac-y tained a predetermined maximum speed;

(7) Has a spring for rotating the synchronous brake and centrifugal means;

(8) Has means for compensating for variations in the driving power of the spiral spring;

(9) Has means for insuring substantially instantaneousv deceleration of the centrifugal mechanism and for preventing the partial incomplete deceleration of said means;

(10) Has means for adjusting the centrifugal mechanism to vary the maximum speed thereof;

(11) Has a resiliently mounted centrifugal weight which is held stationary relative to its revolving support during normal operation;

(12) Has improved means for frictionally and resiliently connecting the centrifugal mechanism to its supporting shaft;

(13) Permits variation in the speed of operation of the clock in synchronism with a current supply of varying frequency without affecting the centrifugal governing mechanism;

(14) Has means for facilitating restarting of the clock upon resumption of the current supply; and

(15) Has means to prevent restarting of the clock when the supply of current is resumed after the spring of the spring motor has run down.

A further object is to provide an improved mechanical speed governing means.

. A further object is to provide an improved centrifugal speed governing mechanism operable to cause the rotating part alternately to accelerate and decelerate between definite maximum and minimum limits and thereby maintain a predetermined average speed of rotation.

A further object is to provide means for rapidly decelerating the centrifugal speed governing mechanism from a predetermined maximum speed to a predetermined minimum speed.

A further object is to provide a synchronous electric clock which will operate during current interruptions, which is simple in construction and operation, and which may be economically manufactured.

Other objects will appear from the following description, reference being had to the accom panying drawings, in which Fig. l is an elevation of the of the face being broken away;

Fig. 2 is a plan view thereof;

Fig. 3 is a rear elevation of the clock;

Fig. 4 is a central vertical sectional'view taken on the line 4-4 of Fig. 3; Fig. 5'is. a fragmentary central vertical sectional view of the centrifugal governor, showing the means for connecting the same to the rotor shaft;

Fig. 5a is an enlarged view taken from the right of Fig. 5 and illustrating the different relative positions which may be taken by the spring and shaft;

Fig. 6 is a developed sectional view, showing particularly the gear trains;

Fig. 7 is a diagrammatic view mechanism;

Fig. 8 is a rear elevational trifugal governing mechanism;

Fig. 8a is an enlarged fragmentary view of a clock, a portion viewv of the cenportion of the centrifugal governing mechanism shown in Fig. 8;

Fig. 9 is a vertical sectional View taken on the line 9-9 of Fig.-8;

Fig. 10 is a rear elevational view of a modified form of centrifugal governing mechanism;

Fig. 1l is a sectional view thereof taken on'l the line ||i| of Fig. 10;

Figs. 12, 13 and 14 show the different forms of stator laminations; and

Fig; 15 is a graph showing the velocity characteristics of a clock incorporating my invention.

General construction In order that the detailed description o'f the clock may be more readily understood, the general features of construction and an outline of the operation will be presented ilrst.

The clock comprises three generally similar frame plates 20, 22 and 244. Studs 26, 2B, 30 connect plates 20 and 22, and studs 32, 34 and 36 join plates Z2 and 24. The clock is of course mounted in a suitable case, not shown, and has a face dial 38, an hour hand 40, minute hand 42. and second hand 44.

Referring to the diagram of Fig. 7, the clock comprises an induction motor having an induction rotor 64, which, through the gear train 1B, 86, 90, 92, 88, |00, |04, |08, ||0 and H2, rotates spring drumv |4. The spring 8, the outer end of which is secured to the Adrum ||4, has its inner end secured to the shaft H6, and through gear train |20. |22, |24, |26. |28, |39. |32. |34, |36 and |38, drives shaft 14. The toothed rotor 10 forms a synchronous brake in cooperation with the toothed poles forming part of a suitable magof the operating l Il clockwise.

yadditional functions.

frame plate 22 by bolts O2, 63.

netic field, and is rigidly secured to the shaft N. Also secured to the shaft Il is a mechanical speed governing mechanism, shown in Fig. 7 as comprising a weight 312 which is resiliently connected to a frame 352 carried by the shaft 14. A pawl |18 cooperates with. the ratchet wheel |16 to prevent clockwise rotation thereof. The hands of the clock are driven from the train of gearing which connects the rotor of the synchronous brake and the shaft |56.

In operation, the induction rotor 64, if unimpeded, would rotate at a speed several times as great as the rotor'lu of the synchronous brake and thus it will be effective to wind the spring ||8 and maintain it wound. When the spring is thus wound, a force will be transmitted to the shaft il@ and hence through the train of gearing to the synchronous brake. Assuming that the synchronous brake has been set in motion at synchronous speed (which is accomplished manually), the induction rotor will, through the two trains of gearingand through the spring I It, continue to rotate the synchronous brake and also thecentrifugal mechanism which is resiliently connected to the shaft 'it and rotatable therewith.

Upon an interruption of the supply of current, the spring E65 will of course tend to rotate the shaft liti countercloclrwise and the spring drum The clockwise movement of the spring drum iid will, however, he arrested in a short time by the pawl llt, se that all of the remaining energy stored up in the spring H8 will be dissipated through driving the train of gearing shown at the right in Fig. '5, and the shaft ll and all parts rotatable therewith. During the periods of current interruption, the synchronous hraire is of course not effective to control the speed of rotation. of the shaft 14. During this period, however, the centrifugal mechanism accomplishes this function, the pawl |78 arresting clockwise movement of the ratchet wheel l'l'E so that the spring H8 effective to rotate shaft HB and through the connecting gear train rotate the shaft 14.

As will hereinafter appear, the centrifugal mechanism, which includes the frame 352 and its resillently mounted weight 312, governs the speed of rotation of the shaft li and performs all of the functions of a balance wheel or pendulum escapement mechanism, as well as several The induction motor and the synchronous brake The coil 60, which is adapted to be connected to a suitable source of alternating current by conductors 52 and plug 54, is wound about the inwardly projecting ends of laminations 53, 55, 50, 51, 58 and 59 (Figs. 3, 4, 12, 13 and 14) which are secured to each other by bars 80 and to the The laminations 56 and 58 are substantially E-shaped, the ends vof the two lower horizontal portions of these er torque which itis capable of developing. The term "induction motor isl used in the specification and in the claims to distinguish the mocured to the shaft 14.

tor, which comprises the rotor M and field lami- 7 nations BC, 5l, from the spring motor, and the term should be construed broadly to define any self-starting motor capable of developing torque throughout a wide range of speeds. The laminations of the unshaded poles are preferably secured against vibration by bolts or rivets 68. The inner laminations 5l, 59., of which there are several pairs, have diametrlcally opposite inwardlyv projecting -portions 51' and 59' which form poles for the rotor l0 of the synchronous brake. These poles are toothed to register with the teeth formed upon the rotor 1G, as shown in dotted linesY in Fig. 3. A plurality of pairs of laminations 53, 55 are positioned between the laminations 56, 58 and 51, 59, respectively, forming spacers therefor.

The rotor 10 may be solid or may be formed of two or more identical laminations secured to a hub l2, the latter being non-rotatably secured to a shaft 14.A The rotor M of the induction motor is pressed over a pinion 16 which is freely rotatable upon the shaft 14. The shaft 14 is rotatably mounted in suitable bearings formed in plates 18, secured to frame plate 24 and bearing plates 82, 8| secured to frame plate 22.

These bearing plates are made of a phenolic condensation product or similar material.,

The gear trains andfspring motor As best shown in Figs. 4, 6 and 7, the pinion I6 is in mesh with a gean B6, which is secured on a sleeve 81 and freely rotatable upon a shaft 88, and has a pinion 9|! secured thereto. The pinion 9d meshes with a gear 92 secured to a sleeve 94, which is rotatable upon a shaft S6. The opposite end of the sleeve 94 has a pinion 98 secured thereto meshing with a gear we which is rigidly secured toa shaft |02. The gear im! carries a pinion EN. which meshes with a gear 06, the latter being freely rotatable upon a shaft |08 and vcarrying a pinion llc. The pinion lit meshes with a gear ||2 formed on the spring drum H4, the latter being mounted for free rotation upon the spring shaft H6. A spiral clock spring l I8 has its outer end secured to the spring drum and its inner end secured to the shaft H6.

The above described gear train thus is adapted to transmit power from the induction rotor 64 to the spring drum to Wind the same, or rather, in normal operation, to maintain the same wound. A similar gear train is utilized for transmitting the power of the spring to the synchronous brake. This-gear train comprises gear |20 secured to the shaft IIE and meshing with pinion |22 secured to shaft |08. The pinion v|22 is rigid with a gear |24, the latter meshing with the pinion |26, freely rotatable on the shaft |02. A gear |28 is xed to the pinion |26 and meshes with a. pinion |30, the latter being fixed to shaft ll. The opposite end of the shaft 96 has a gear |32 secured thereto, the latter meshing with a pinion I secured to the shaft 88. A gear 36, rigid with the pinion IN, drives a pinion |38 se- As previously stated, the rotor 1l is rigidly secured to the shaft 14. The last described gear train is thus adapted to transmit the driving energy of the spring ||8 to the rotor assembly of the synchronous brake. 'I'he rotor 64 of the induction motor and the rotor 'l0 of the synchronous brake rotate lin the same direction, and it will be noted that corresponding gears'of the two trains are in each instance mounted on -the same axis, and since the gear ratios are identical, each gear which is rotatable on a shaft will, during normal operation of the 'be' necessary. Due to the improved bearings which I have provided for the ends of the shafts,

t the wear upon bearings has been greatly reduced and the clock mechanism made more durable. It will be understood that the only time when the gears which are rotatably mounted upon -a shaft rotate relative to the shaft is during intervals of current interruption when the train of gearingbetween the rotor 84 ofthe induction motor and the spring drum ||4 is stationary, and following an interruption when the spring is rewound.

' The gearing ratio is such that the shaft |08 will rotate at one revolution per minute, and the seeond hand 44 may therefore be secured to the end of this shaft. The shaft |08 has a pinion |40 secured thereto which meshes with a gear` |42 rotatably mounted upon ay shaft |44. 'I'he gear |42 is rigidly connected to a pinion |48'which meshes with a gear |48 rotatably mounted upon the shaft |08. The latter gear is rigidly connected tov a sleeve |50 surrounding the shaft |08 and at its end carrying the minute hand 42. The

y gear |48 is frictionally rotated with the shaft |08 by a spider spring |48 compressed between the pinion |40 and the side of the gear |48. The

pinion |52 secured to the gear |48 meshes with agear |54 secured to the shaft |44. The gear |54 has a pinion |55 secured thereto and projecting outwardly through the frame 20,` the pinion |56 meshing with a gear |56 secured to the hour hand -sleeve |60. It will thus appear that the time inoutwardly to form a lug 368. A leaf spring 31| has one end riveted to the lug 368 and at its opposite end has a small weight 312 secured thereto. Y Y

An adjusting screw 314 passes freely through a suitable aperture in the spring 310 and is threaded in a lug 316 struck outwardly from the side of the cross-piece 360. 'I'he head of the screw normally holds the spring in the position shown in Fig. 8 with the weight 312 resiliently held against a stop lug 318 which is bent outwardly at the end n of arm 358. Outward movement of the weight v312 under the influence of centrifugal force, is

limited by a stop 380 bent outwardly from the cross-piece 360 and engageable with the spring 310 adjacent the weight 312.

T'he frame is secured against more than a limited degree of rotation relative to the shaft 14 by means of a wire spring 382. This spring passes through a suitable aperture formed in a lug 384 struck up from the arm 356 through a relatively large hole 386 formed in the shaft 14 and has its other end positioned in an L-shaped notch 388 formed in a lug 390 struck up from the arm 362. The spring is held against longitudinal movement by the lug 368 and a lug 392 struck up from the arm 362. I'he spring is bowed so that it normally pulls the frame 352 to the right (Figs. 4 and 5) so that the hub 354 presses l ment of the frame.

and 24 and carrying a pinion |12, adapted to mesh with gear |32 when the thumb piece |68 is pushed inwardly. A spring |14 normally holds the pinion |12 disengaged from the gear |32. This thumb piece isv used only in starting the clock, as will hereinafter appear.

The drum I4 of the spring motor has a ratchet wheel |16 secured thereto or formed integrally therewith. A spring pressed pawl |18 is engageable with the teeth of the ratchet wheel |16 to prevent clockwise (Fig. 7) rotation thereof. If desired, a so-called silent pawl may be substituted for the spring pressed pawl |18.

The centrifugal brake mechanism The centrifugal brake mechanism shown in Figs. 4, 5, '7, 8 and 9, comprises a hub 354 which is freely rotatable upon the shaft 14 and which is rigidly secured in a frame 352. The frame 352 is preferably made of a light metal such as aluminum, and comprises arms 358 and 358 joined at their ends by a cross-piece 388, and arms 362 and 364 joined at their ends by an arcuate section 368. The extremity of the arm 356 is bent against a washer 394 which is mounted on the shaft 14. The washer 394 is preferably made of a phenol condensation produce or similar substance.

It will be noted that the hole 386 in 4the shaft through a slightly greater angle relative to the shaft 14 than thespring wire 382 since the latter will bend slightly to permit such additional move- The spring 362 thus serves as a means to cause a definite amount of friction between the frame 352 and the shaft 14 and also serves as a resilient driving connection between the shaft and the frame. The frame is statically and dynamically balanced for `rotation at its normal speed, a suitable counterweight 396 secured to the arcuate section Y366 being provided for this purpose. 1 I

It will be noted that the spring 310 extends a slight distance beyond the weight 312. This end portion of the spring is adapted, when the frame v 352 is rotated above its normal synchronous cured to a bushing 400 carried on'the end of shaft 402. The shaft 402 is rotatably mounted in the frame plates 22 and 24 but is urged to rotate counterclockwise (Fig. 8) by a torsion spring 404, one end of which is anchored to the shaft and the other end of which is anchored and hard so that the tip 408 will, if it is revolving in a position to strike the extreme edge of `the arm, engage and move the arm instead of striking thelatter a glancing blow.

Operation.

Assuming that the plug 54 has been connected to a source of alternating current of regulated frequency, the operation of the clock is as follows: As soon as a connection with the source is made, the rotor 64 of the induction motor, due to the rotating field formed by the shaded poles of the laminations 56, B, commences rotating, and through the gear train between it and the spring drum III commences winding up the spring il 8. brake will be held stationary by the magnetic flux since its field is not rotating, but on the 'contrary its pole pieces have teeth which register with and attract the teeth of the rotor. .The spring, even whenlfully wound up, is notsuiliciently strong to move the rotor 'lll of the synchronous brake out of its magnetically locked" position. Thus, unless the synchronous brake l is moved from its locked position, the induction rotor 54 would continue to operate until the spring Ht was fully wound up.

The user is instructed, after he has connected the plug Si in a suitable socket, to push in and rotate the thumb piece 188 clockwise. When the thumb piece is pushed in, the pinion |12 connected to its stem llc engages the gear i3! so that when the thumb piece is manually twirled, the shaft 'iii and all parts connected therewith are rotated, the rotor Moi the synchronous being forcibly moved out of its magnetically locked position. ils soon as the rotor rof-is the rotor approaches synchronous speed its magnetic held exerts a powerful torque upon it, but unless the teeth of the rotor are exact phase with the alternating current it will tend to pass right through synchronism. 1f, however, the teeth of the rotor are in exact phase with the alternating current at the time the rotor is at synchronous speed it will then continue to operatein synchronism. Unless some means are provided to dissipate energy at the instant that the rotor arrives at synchronous speed, Athere is aprobability that the rotor will not fall into step. The theory and principles of the operation ofthe rotor with reference toA its coming into synchronism are substantially the same as those of a similar rotor of a synchronous motor, such, for example, as is shown and described in Patent No. 1,719,805, granted to me on July 2. 1929. In the present construction, the frame 352 and all parts carried thereby constitute the inertia member and correspond to the inertia washer disclosed in said patent. It will be noted that the frame 352 is frictionally connected to the shaft 14 normally to rotate therewith by means of the frictional engagement of the hub The rotor 10 of the synchronousV at appreciable speed, the poles of the subsequent operation at super-synchronous speed l 354 with the friction washer $94 caused by the bowed spring 382. The friction between these parts should be considerable, but should be small enough to permit relative motion between the parts when the rotor falls into step. The spring 382 has sufiicient play in the hole 3" and is suillciently pliable that it does not materially interfere with the utility of the frame 352 and parts carried thereby as an inertia means to velocity ci the chart will lie insure falling into step of the rotor I0 of the synchronous brake, but of course causes the frame 352 and associated parts to rotate with the shaft 'I4 except for such minor relative movement as is desirable to cause the rotor of the synchronous brake readily to fall into step and to prevent it from hunting.

Having brought the synchronous brake rotor 10 up to synchronous speed, it will continue to be driven by the spring iis and will act as a nearly perfect governor to control the speed of unwinding of the spring in synchronism with the frequency of the alternating current supply. The rotor 64 constitutes a variable speed motor which is of the induction type. It is capable, however, of running at a speed several times the synchronous speed of the rotor l0, so that even though the rotor i0 is started substantially at the same time that the clock is connected to a source of alternating current, it will within a short time completely wind the spring H8, or at least will wind the spring to an extent where the torque from the spring tending to rotate the rotor B4 in a reverse direction is exactly equal t0 the torque developed bythe rotor @it when rotating at the same speed as the rotor lil. While the clock is tinus operating the centrifugal impulse governing mechanism will operate idly, the

Weight 3l@ being held against the stop Slt by the circus accordance the cur- 'the answer reinaiter be er:- pressed in units ci such value that its numerical value wilt be the same as the current frequency which would, through the control of the synchronous braise, cause it to rotate at such velocitye. g., when the frequency of the current supplied to the synchronous brake is 60 cycles per second the shaft 14 will have an angular velocity, or speed, of 60.)

While the frequency of the current supplied by well regulated power stations will seldom vary more than 1% above or below its nominal frequency, occasional sudden application of heavy loads or breakdown of one of the generators in the station may cause the frequency to drop considerably below the normal as indicated by the drop at C in the diagram of Fig. 15. Such a drop in frequency will not, however, affect the centrifugal governor, and unless the current is interrupted, the governor will not interfere with (ller necessary to regain the time "lost as a result of the drop in frequency. AWhile the frequency may occasionally drop greatly below the nominal frequency, it will seldom, if ever, greatly exceed the nominal frequency, since generator speeds greatly in excess of their normal speed, might readily result in damage to the prime movers, generators and other power station equipment.

It will be assumed that the generators are equipped with governors or other safety devices which will absolutely preclude them from rotating at a speed higher than that necessary to generate 65 cycle current. Under such conditions, which are substantially those normally encountered, itwill be desirable to provide a mechanical speed governing means for the clock which would not interferel with the normal 'operation of the clock under the control of the synchronous brake throughout a range of to 65 cycles but which would be effective, upon a current interruption, accurately tc control the speed of shaft 14 so that its average speed will be 60. It is of course desirable to accomplish this without the use of complicated electromagnetically operated brakes, clutches, etc., since such complications in the apparatus lead to inaccuracies and uncertainties in operation. The centrifugal impulse governor previously described possesses these desiderata.

The centrifugal impulse governor operates upon the principle that a body starting at a given minimum velocity, accelerating at a constant rate to a predetermined maximum velocity, and decelerating at a constant rate to the said minimum velocity, will have an average velocity equal to the mean between the maximum and minimum velocities, irrespective of the rates of acceleration and deceleration. Referring to the diagram oi' Fig. l5, the average angular velocity of the shaft 14 will be maintained at 63 when rotating as represented by the broken line BD, even though rates of acceleration for individual cycles of acceleration` and deceleration may differ. 'Ihus the average angular velocity during the cycle EFGH will be the same as during the cycle IJKL even though, as is obvious, the rates of acceleration of these two cycles of operation dier considerably.

Upon an'interruption in the supply of current to the synchronous brake, the main springA H3 will transmit its power through the gear train to shaft 14 and, since the spring is capable of exerting a torque greater than the counter-torque due to friction in the gear'train, will accelerate ity 313 of the spring 313 that it is practically impossible for the latter to strike the former a glancing blow. If the said extremity contacts only with the extreme end ledge of the arm 333, the resultant forces are such that the spring 'will be outwardly (from the axis of shaft 14) lflexed and thus be moved to a position where it will contact with arm 393 farther from the end edge 0f the latter. Thus the lextremity 313 either properly hits the arm 393 or misses it entirely.

When the extremity 313 strikes the arm 333 th stop aso limits its outward movement, thus precluding the possibility of the spring 310 being bent beyond its elastic limit. After striking the arm 393 the spring 310 and weight 312 would have a tendency to vibrate relative to the frame 352 were it not for the provision of the stop lug 313 which acts as a damper. The energy which would otherwise set up vibration is quickly dissipated upon impact of the weight 312 against the stop lug 313. The possibility of the extremity 313 striking the arm 393 Awhen the frame 352 is not rotating at its predetermined maximum speed is thus. eliminated.

The predetermined maximum velocity (at which the arm 393 will be struck) may be changed with a very high degree of accuracy by adjustment of the screw 314.; Changing the maximum velocity will of course result in a corresponding change in the a'verage velocity.

It will be observed thatJ as themain spring H3 becomes unwound its power decreases and the rate at which'it can accelerate the centrifugal governing mechanism correspondingly decreases, but that this doesA not have anyeil'ect upon its governing or timekeeping qualities. Since the deceleration is very rapid, being nearly l instantaneous, the force of the main spring H3 the shaft 14 and all parts operatively connected therewith. Assuming that the current was interrupted at B (Fig. 15), the shaft will ac-v celerate until it attains a speed of 65 represented by the point M (Fig. 15).

When the frame 352 attains the maximum speed of 65 the spring 31)V will be flexed outwardly to the dotted line positions (Fig. 8) by centrifugal force acting on the weight 312, and its extremity 313 revolved in the path represented by the dotted circle 315. When traveling in this path the extremity will just strike the extreme end edge of the arm 393. This spring pressed arm and its connected parts have exactly sufficient inertia, and its spring 494 sufficient tension, that when the arm is thus struck by the end of spring 310, kinetic energy will be transferred from the spring 313 (and parts operatively connected therewith) to the arm 393 (and parts operatively connected therewith) in an amount exactly equal to that necessary to vreduce the speed of the shaft to 55, the minimum velocity.

'Ihis transfer of energy takes place substantially is practically eliminated as a factor during this phase of the operating cycle.

Throughout the'period of current interruption the centrifugal governing mechanism will repeatedly operate in-themannei' above described, and as diagrammatically illustrated in Figure l5. Upon resumption of the current supply. the synchronous brake will become effective as soon as its rotor 1.0 is accelerated to its synchronous speed. the frictional and resilient connection between the frame 352 and the shaft 14 aiding the rotor to fall into step. If perchance the rotor should not fall into step the first time it approaches synchronous speed, it will have innumerable additional opportunities to fall into step during the accelerative phase of subsequent cycles of operation of the centrifugal governing mechanism. It is improbable vthat the rotor will wall into step during the decelerative phase-of the cycle because the deceleration occurs .so rapidly.

The centrifugal governing mechanism, as above set forth, has a large number of advantages when used in combination with a synchronous electric clock, but obviously is useful in other timekeeping and speed governing mechanisms.

Modified centrifugal governing mechanism f In Figs. 10 and 11, I have illustrated a modied form of the centrifugal impulse governing mechanism. This mechanism operates upon substantially the same principles as the mechanism above described. It comprises a rotor shaft 41 having a head 204 secured at the, end thereof, and having a bar 132 rotatably mounted on the shaft but normally rotated therewith by means of the wire spring 209, the ends of which project into openings 2|0 formed in the bar |92 and the mid portion of which engages in a slot formed in the head 20N. The bar |92 has a pair of arms |99 to which are secured a pair of leaf springs I96. Weights 200 are secured a short distance inwardly from the freey extremities of the leaf springs |96. The extremities of the leaf springs are adapted, when swung outwardly by centrifugal force, to engage the teeth 330 oran inertia wheel 302 which is rotatably mounted upon a shouldered stud 934. Assuming that the shaft 14 rotates counterclockwise (Fig. 10), the teeth 330 will have substantially radial faces in position to be struckby the extremities of the leaf spring |96c. ,The arms |93 are Iarcuately shaped so that their extremities form fixed stops for the leaf springs |99c and thus hold the weights loutwardly a slight distance beyond that which they would assume when revolving at their normal synchronous speed. IThe arms thus serve the same purpose as the stop 318 in the previously described embodiment, and serve as energy dissipating means to damp vibratory motion or the weights.

It will be understood that the mechanism shown in Figs. lo and il is adapted to be substituted for that shown in Figs. 8 and 9, and that the shaft' 'Mc corresponds to the shaft 'lli in the previously described embodiment. The operation of this mechanism .is substantially the same that eause the ends of wheel. The maxim anisn'i may readily be adjusted ey .means screws 342. .Adjustment of the maximum velos ity will of course effect a corresponding variation in the average velocity. In this embodiment as well as in that previously described, the transfer' of energy takes place substantially instantaneously upon the impact of the extremity of the veia-city spring |96c with a tooth of the wheel 332, and

therefore the amount of energy transferred from the rotating part of the mechanism to the wheel 902 is dependent substantially whollyupon the u This embodiment relative inertias of the parts. as well as that previously described has the advantage that the centrifugal mechanism operates idly during normal operation and is only eifecti ve to control the speed of operation of the clock during intervals of current interruption. During the current interruptions the mechanism will make a slight noise which will serve the useful purpose of indicating that the current supply to the clock has been interrupted.

In the modified form of Figs. 10 and 11 as well as in the preferred construction, the spring may be constructed so as to be capable of driving the mechanism for a period greatly exceeding in duration any usual current interruption. However, should the current be interrupted for a period suillciently long to permit the spring 0 completely to unwind, and theclock to come to a stop, the clock will not again start upon resumption of the supply of current and will thus, by the fact that it is not going, indicate that it is showing the incorrect time.

unusual extended current interruption, it will be necessary to reset the hands of the clock and 75 After such an restart it by manually twirling the thumb piece |99.

While I have illustrated and described the preferred embodiments of my invention, many modiflcations may be made without departing from the spirit of the `invention, and I do not wish to be limited to the precise details set forth but desire to avail myself of all changes within the scope of the appended claims. 1

I claim:

1. In a time-keeping device, the combination of a shaft, a synchronous electric rotor rigidly Cle tor cooperating secured to said shaft and a centrifugal governor rotatably mounted on said shaft, and a frictional and resilient driving connection between said governor and said shaft.

2. In a time-keeping device, the combination of a motor, a shaft driven thereby and means for controlling the speed of rotation of said shaft comprising a weight, a spring forming the sole means movable with respect to said shaft for securing said Weight to said shaft, said weight being adapted to be moved outwardly from the axis of said shaft by centrifugal force, and movable impulse receiving means to impede rotational movement of said weight when the latter is moved a predetermined distance from the axis oi said shaft.

3. In a time-keeping device, the combination of a coil adapted to Toe connected to la source of alternating current, a core for said coil having a plurality oi i' ction ro oi poles,

an energy storii synchi g moto of poles,

kof said energy sto chronous braise fi. in an electric rolled and operated timing device, the combin on of a spring motor, electric motor means to wind said spring motor, gearing driven by said spring motor, an electromagnetic mechanism driven by said gearing and maintained in synchronism with the alternations of electric current from a source of regulated frequency, a magnetic eid producing means connected to said source for energizing both said electric motor means and said electro-magnetic mechanism, and continuously operating mechanical means for controlling the speed of operation of said spring motor upon interruption of the current supplied to said electro-magnetic mechanism.

5.- Means for controlling the speed of operation of a rotating part comprising a synchronous brake connected to a source of alternating current, a centrifugal governing mechanism connected with the moving part of said brake to control the speed of operation of said rotating .part upon interruption of the supply of current to said synchronous brake, and a resilient and frictional 'connection between said centrifugal governor and the moving part of said synchronous brake whereby the connection will serve as an energy dissipating means to aid in causing the synchronous brake to fall into synchronlsm with the source of alternating current and to minimize hunting of the synchronous brake.

6. In a time-keeping device, the combination of a synchronous electric brake having a rotatable part, power means for rotating said part of said brake, a member rotatable with lthe rotatable part of said synchronous brake, centrifugal force operated means for moving said member relative to its axis-of rotation, resilient means resisting the centrifugal force applied to said member, and an element positioned so as to be moved by said member when the latter'is moved outwardly by centrifugal force resultant from rotation at a speed substantially greater than the synchronous speed of4 said synchronous brake, the inertia of said element being so great relative to the inertia of said member and the parts movingtherewith that the latterwill be rapidly decelerated to a velocity less than the synchronous speed upon impact of said member with said element and transmit a substantial portion of their kinetic energy to said element.

7. A speed governing mechanism for maintaining a constant average speed comprising a member, the speed of which is to be governed. means for repeatedly accelerating said member from a given minimum velocity, and means for repeatedly decelerating said member to said given minimumvelocity whenever the member reaches a predetermined maximum velocity, the range of variation in the instantaneous velocity of the member being great compared with the range of variation of its average velocity.

.8. A time-keeping device comprising a shaft, variable power means for rotating said shaft, a weight, means includinga resilient element for securing said weight to said shaft eccentric of the axis of the shaft, and a peripherally notched wheel mounted for rotation at a point adjacent the path of revolution of said weight and adapted to receive a rotative impulse from said weight when the latter has attained a predetermined velocity of revolution, thereby to reduce the speed of rotation of said shaft.

9. A time-keeping device comprising a variable torque motor, a shaft connected to be driven thereby, a weight, means including a resilient element for securing said weight to said shaft eccentric of the axis thereof, a peripherally notched wheel, an adjustable pivotal support for said wheel, and means moved by said weight and engageable with said wheel when said shaft is rotating at a predetermined speed, thereby to impart to said wheel a portion of the kinetic energy of rotation of said shaft and parts rotating therewith.

A10. A time keeping mechanism comprising motor means, a member mounted for movement by centrifugal force and revolved by said motor, and means` for rapidly dissipating a predetermined substantial portion of the kinetic energy si said member whenever it attains a predetermined speed of revolution, said means being of such mass and construction, relative to the eiective driving vforce of said motor means and the rotary moment of inertia of said member', that said-,means will be effective to reduce the speed 'of said -member to 'a velocity such that it will take a number of revolutions of the latter to accelerate to a-speed lat which said means again becomes elfective.

11'. A timekeeping mechanism comprising motor means, a member mounted for movement by centrifugal force and revolved by said motor means, means for rapidly dissipating a predetermined substantial portion of the kinetic energy of said member whenever it attains a predetermined speed of revolution, and' means for damping vibratory movement of -said member.

12. A time keeping mechanism comprising motor means, a member mounted for movement by centrifugal force and revolved bysaid motor, and

means for rapidly dissipating a predetermined substantial portion of the kinetic energy of said member whenever it attains a predetermined speed o f revolution, said means comprising an element of appreciable inertia movably mounted in the path of movement of said member, the torque of said motor means, the rotary moment of inertia of the means driven therebyincluding said member, and the energy dissipating capacity o! said means being so correlated that a number of revolutions of said member will be required for said member to accelerate from the speed to which it is reduced by said energy dissipating means to said-predetermined speed.

13. A time keeping mechanismcomprising mos tor means, a member mounted for movement by centrifugal force and revolved byv said motor means, means for rapidly dissipating a predetermined substantial portion of the kinetic energy of said member whenever it attains a predetermined speed of revolution, said means comprising an element of appreciable inertia, and resilient means to hold said element in the path of revolution of said member when the latter is revolving at its said predetermined speed.

14. A time keeping mechanism comprising a passing through the axis of revolution of said member.

15. A time keepingmechanism comprising a" spring motor, a member mounted for movement by centrifugal force and revolved by said motor, resilient means opposing the action of centrifugal force on said member, means to vary the force vexerted by said resilient means, and means for dissipating a predetermined substantial portion of the kinetic energy of said member when the latter attains a predetermined maximum velocity;

16. A time keeping mechanism comprising a spring motor, a member mounted for movement by centrifugal force and revolved by said motor, resilient means opposing the action of centrii'ugal force on said member, means to vary the force exerted by said resilient means, means for dissipating a predetermined substantial portion ofv the kinetic energy of said member when the latter attains a predetermined maximum velocity, and means to damp vibration of said member. a

17. In a time keeping device, a shaft having a hole passing diametrically therethrough, a frame rotatably mounted on said shaft, said frame having lugs thereon spaced from said shaft, a friction washer on said shaft between said frame and the hole in said shaft, and aresilisnt wireA secured to said lugs and passing through said hole, said wire-being bowed to draw said frame against said friction washer.

18. In a time keeping device, the combination of a shaft, a frame rotatably mounted on said shaft, a friction member on said shaft, and a single spring cooperating with said frame and shaft and operative resiliently to connect said frame to said shaft for conjoint rotation, tohold said friction member on said shaft and to hold said frame' against said friction member.

19. In atime keeping device, the' combination of a shaft having a diametrical hole therein, a member rotatably mounted thereon, and s. resilient wire of appreciably smaller diameter than said hole and passing therethrough. the ends of said .wire being secured to said member, whereby said spring forms a resilient lost motion connection between said shaft and said member to permit limited relative rotative movement there-4 Ibetween.

20. In a centrifugal governor for maintaining the speed of rotation of a member at a substantially constant predetermined average value despite a variation in the value of the driving force, a movable centrifugal element adapted to move outwardly from its axis of rotation upon an increase in speed, a normally stationary stop adapted to be struck when said centrifugal element moves outwardly toa position corresponding to a velocity considerably in excess of said predetermined average value to be maintained, f

and mounting means for said stop permitting the stop to move away under the inuence of the stroke and thereby rob the rotating system in a single impact of an appreciableamount of its total kinetic energy of rotation.

21. In combination, a centrifugal governor for maintaining the speed of rotation of a member at a substantially constant predetermined average value despite a variation in the value of the driving force, said governor comprising a movable centrifugal element adapted to move outwardly from its axis of rotation upon an increase in speed,l a normally stationary stop adapted to be struck when said centrifugal element moves outwardly to a position corresponding to a velocityconsiderably in excess of said predetermined average value to be maintained,mounting means for said stop permitting-the stop to move away under the 'influence of the stroke and thereby rob the rotating system in a single impact of of rotation; and an independent electro-magnetic governing mechanism for limiting the speed of said rotary member to said predetermined average value, said mechanism being operable to maintain said governor at a speed at which said element will not strike said stop.

22. In combination, a centrifugal governorfor maintaining the speed of rotation of ay member at a substantially constant predetermined average value despite a variation in the value of the driving force, a movable centrifugal element adapted to move outwardly from its axis of rotation upon an increase in speed, a normally stationary stop adapted to be struck when said centrifugal element moves outwardly to a position corresponding to a velocity considerably in excess of said predetermined average value to be maintained, mounting means for said stop permitting the stop to move away under the influence of the stroke and thereby rob the rotating system in a single impact of an appreciable amount of its total kinetic energy of rotation, and a second governor normally operable to maintain said member at substantially said predetermined average speed, said second governor being constructed while operative never to permit said member to attain the said predetermined maximum speed.

23. In combination with an electrically wound clock mechanism, a synchronous brake rotor forming the escapement mechanism thereof, and a centrifugal speed governing mechanism rotating with said rotor and effective upon discontinuance of the operation `oi said synchronousbrake rotor to control the speed of operation of said clock mechanism.

24. A timing device comprising a mechanical motor, a time movement connected so as to be operated by said motor, a non-self-starting synchronous motor having its rotor connected in reversible driving relation with said movement, and a speed responsive mechanical governing device connected in driving relation with said movement, the latter becoming effective at a speed slightly above the normal speed of the movement, as determined by the speed of the synchronous motor, to momentarily reduce the speed slightly below normal.

25. A timing device comprising a mechanical motor, a time movement connected so as to be driven by said motor, and a pair of speed governing devices for said movement, one of said governing devices comprising a non-self-starting synchronous motor having its rotor connected in driving relation with said time movement for causing the time movement to operate at its normal rate of speed when the synchronous motor is operating as such at its synchronous speed, the other governing device comprising a centrifugal speed checking device connected in driving relation with said movement and adjusted to become effective when the speed of the time movement is slightly above normal to momentarily reduce the speed to slightly below normal, the latter governing device serving to maintain the average speed of the time movement at approximately its normal value when the rst mentioned control device is ineffective.

26. A timing device comprising a spring motor, a time movement connected to be driven by `said spring motor, a pair of rotary speed governing devices for said time movement, both continuously connected in reversible driving relation therewith, one of said devices comprising a synchronous motor effective when energized at its normal frequency to maintain the rate of the time movement correct, and the other device comprising a centrifugal' `speed checking device effective when the synchronous motor is deenergized to maintain the average rate of the time movement substantially correct, said centrifugal speed checking device being of a type which may ,be driven at speeds considerably above and below the average speed which it is capable of maintaining, without having any speed controlling Veffect whatsoever upon the means driving it.

resisting such movement of said part, yielding means to hold said elementin the path of movement of said part when the latter has moved outwardly a predetermined extent. said part being adapted to engage said element when the former reaches a predetermined velocity which is considerably in excess of the average velocity to be maintained, and yieldable means to rotate said member.

. 28. In an electrically wound clock, the combination of a synchronous rotor connected to the clock so as to form an escapement mechanism therefor, and a centrifugal governing mechanism rotated with said rotor, said mechanism being ineffective to perform its function when said rotor is operating at synchronous speed.

29. In a time-keeping device, the lcombination of driving meansan electric synchronous brake driven thereby, said brake having a rotor, a centrifugal speed governing mechanism having a rotating part, said mechanism being ineffective to perform its function while said synchronous brake is eiective, and 'a resilient and frictional driving connection between said rotor and said rotating part.

30. In a time-keeping device adapted to be operated and have its speed controlled from a source of alternating current of regulated frequency. the instantaneous frequency of which may vary but the average frequency of which is constant with a high degree of accuracy, a nonself-starting synchronous motor connected to said source, said motor normally operating as a brake, a rotary centrifugal governor of a type which maintains a constant average velocity while permitting wide fluctuations in instantaneous velocity, a non-slipping driving connection betweensaid synchronous motor and said centrifugal governor, electric motor means' to drive said synchronous motor and said governor under normal conditions while current of regulated frequency is being supplied from said source, and energy storing means connected to drive, said synchronous motor and governor upon interruption in the supply of current of regulated frequency from said source.

31. In a time-keepingl device adapted to be operated and have its speed controlled from a source of alternating current having its cumulative frequency regulated by a time standard, a

synchronous motor connected to said source and operable as a brake, a rotary centrifugal governor of a type which maintains a constant average velocity while permitting Wide fluctuations in instantaneous velocity, means interconnecting said synchronous motor and governor to cause the same to rotate together at a predetermined average speed determined 'by said synchronous motor during the time While current-is being supplied from said source and-determined by said governor during periods of interruption in the supply of current from said source, and means for mechanically driving said synchronous motor and governor.

32. In combination, an induction rotor, an energy storing and releasing motor operatively connected thereto, a synchronous brake rotor mounted adjacent and coaxial with said induction rotor and connected to be driven by said energy storing and releasing motor, and common means for producing a magnetic eldfor both of said rotors.

33. A clock comprising a time movement, a spring for driving said movement, an alternating current motor device for winding said spring and controlling the rate of said movement, said motor device comprising a single phase eld element having parallel magnetic paths, one path producing a rotating magnetic field and the other path producing a pulsating magnetic field, a self-starting rotor element within the inuence of the rotating magnetic eld connected to wind the spring, a non-self-starting synchronousrotor element within the influence of the pulsating eld connected to the time movement for synchronously restraining the time movement to operate at its correct speed, and a centrifugal governor device driven with said time movement and acting in opposition to `the accelerating influence of the spring motor for intermittently reducing the rate of the time movement from above to below normal when the synchronous motor is deenergized.

LAUBENS HAMMOND.

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